The present invention relates to a light beam sensor to be used for an automatic door sensor, a burglar sensor and the like. Particularly, the present invention relates to an improved adjustment mechanism for adjusting the optical axis of an optical unit having an optical element and for adjusting its detection area, wherein such adjustment is operated by changing the posture of the optical unit.
As a conventional automatic door sensor, an auxiliary safety sensor is installed in the vicinity of the track of a door, as disclosed in Japanese Patent Laid-open Publication No. 2000-320243. For example, where a pair of posts stand on both sides of a doorway, a transmitter is mounted on one of the posts and a receiver is mounted on the other post in an opposed manner. The transmitter is equipped with a transmitter unit which internally contains a transmitter element and a transmitter lens. Also, the receiver is equipped with a receiver unit which internally contains a receiver element and a receiver lens. When a light beam (e.g. infrared ray) is emitted from the transmitter unit towards the receiver unit but interrupted by something, the receiver element in the receiver unit fails to receive the light beam. The sensor regards this condition as the presence of a person or other object near the track of the door, and keeps the door in the open state.
Regarding this type of sensors, as far as the transmitter and the receiver are mounted accurately, the optical axis of the transmitter unit is aligned with that of the receiver unit, so that the light emitted from the transmitter unit can be received by the receiver unit without fail.
However, if the transmitter and the receiver are not installed in appropriate positions, or if they show manufacturing tolerances between each other, the optical axes of these units are offset from each other. Under such circumstances, the light emitted from the transmitter unit may not be received by the receiver unit. In an attempt to effect fine adjustment of the optical axes of such units, for example, Japanese Utility Model Laid-open Publication No. S55-165272 provides each of the transmitter and the receiver with an adjustment mechanism having a worm gear. Specifically, each unit has a casing which houses a worm wheel and a worm gear meshed therewith. When this worm gear is operated to rotate, the worm wheel rotates and causes swinging movement of the casing. Accordingly, the direction of the optical axis is finely adjusted in each unit.
Nevertheless, as far as this disclosure is concerned, the adjustable angle of the unit (the swinging angle of the casing) is limited in comparison with the amount of rotational operation of the worm gear. Hence, where the optical axis of the unit should be adjusted by a wide angle, the worm gear has to be operated to provide a greater amount of rotation. The additional rotational operation is not only bothering but also extends the time necessary for the adjustment operation.
Apart from the adjustment mechanism with a worm gear, there may be suggested another mechanism in which a relatively small amount of operation can significantly change the angle of the optical axis in the unit. This suggestion requires, however, two types of adjustment mechanisms which should be disposed separately. Considering the enlargement of the entire adjustment mechanism and eventual enlargement of the transmitter and the receiver, this suggestion is not practical, either.
These problems have been recognized in the art, irrespective of whether such sensor is used as an automatic door sensor or as a burglar sensor. Besides, similar problems arise in the case of a so-called retroreflective sensor, in addition to the above sensor in which the transmitter and the receiver locate opposite to each other. Further, a passive sensor which includes a detection area adjustment mechanism also suffers from such problems.
The present invention is accomplished in view of these problems, and intends to provide an adjustment mechanism for adjusting the optical axis of an optical unit and for adjusting its detection area. The adjustment mechanism of the present invention is capable of effecting fine adjustment quickly by a simple operation. This mechanism can be realized without increasing its size.
To achieve this object, the present invention employs an adjuster for changing a posture of an optical unit having an optical element. This adjuster is threaded on its outer circumferential surface in order that a restriction member can latch with the thread. On the one hand, stepped adjustment of the unit posture is conducted by moving the adjuster such that the restriction member climbs over a thread ridge. On the other hand, stepless adjustment of the unit posture is carried out by moving the adjuster in cooperation with its rotation around a central axis thereof, with the restriction member keeping a latched engagement with a thread groove.
To be specific, a first solution is based on an optical sensor which is equipped with an optical unit having an optical element. This optical sensor comprises an adjuster and a restriction member. The adjuster is joined with the optical unit, and the outer circumferential surface of the adjuster is threaded to give a threaded portion. The adjuster is held to be rotatable around a central axis of the threaded portion and to be movable in a direction of changing a posture of the optical unit. The restriction member restricts movement of the adjuster by latching in a thread groove in the threaded portion, and is capable of climbing over a thread ridge in the threaded portion when the adjuster receives an external force applied in a direction of allowing the restriction member to climb over the thread ridge. This arrangement realizes a first adjustment operation for stepped adjustment of the posture of the optical unit, in which the adjuster is allowed to move in such a manner that the restriction member can climb over the thread ridge in the threaded portion. Besides, this arrangement realizes a second adjustment operation for stepless adjustment of the posture of the optical unit, in which the adjuster is allowed to move in cooperation with its rotation around a central axis thereof, with the restriction member keeping a latched engagement with the thread groove in the threaded portion.
According to this feature, the adjuster serves as a functional component for coarse and fine adjustment of the posture of the optical unit. Namely, the posture of the optical unit can be adjusted both coarsely and finely by a single adjustment mechanism, instead of using two separate adjustment mechanisms. As a result, a compact adjustment mechanism is achieved.
With respect to a second solution based on the first solution, the adjuster is held to be revolvable around an axis line which extends substantially perpendicularly to the central axis of the threaded portion, and the posture of the optical unit can be changed by revolving the adjuster around the axis line. In this solution, the adjuster has a barrel shape in which an outer circumferential surface has an arcuate shape whose center coincides with the axis line.
According to this solution, while the adjuster revolves around the axis line in order to adjust the posture of the optical unit, the arcuate-shape outer circumferential surface of the adjuster maintains a constant positional relationship relative to the restriction member. In this situation, the contact pressure between the adjuster and the restriction member remains unchanged. Hence, no matter where the adjustment position may be, the restriction member is allowed to climb over a thread ridge in the threaded portion in a stable manner.
With respect to a third solution which is based on the first or second solution, the restriction member is composed of a member which is elastically deformable between a latched state in which the restriction member is latched in the thread groove of the adjuster, and a retreated state in which the restriction member is retreated with respect to the adjuster so as to climb over the thread ridge.
According to this solution, when the restriction member climbs over a thread ridge in the threaded portion during the first adjustment operation, the restriction member elastically deforms in the direction of retreating from the adjuster. The elastic deformation allows the restriction member to climb over the thread ridge smoothly. After the completion of the first adjustment operation, the restriction member fits into the thread groove in the threaded portion and restricts the posture of the adjuster again.